Typically, power devices, which include an integrated circuit, used in combination with a printed circuit board, require significant heat dissipation as a result of the large power build-up in the integrated circuit. This power build-up results in special design requirements for heat-sinking the power device. Accordingly, substantial assembly time and costs result from the heat sinking design requirements.
Traditionally, power devices are attached to a printed circuit board by means of "thru-hole" technology. Using this technology, the ends of electrical connectors from the power device are inserted through holes in the printed circuit board and the electrical connectors are either manually soldered or secured by a leaded insertion machine in combination with a wave solder machine to the opposite side of the printed circuit board. Alternatively, the electrical connectors can be "surface mounted", i.e. the electrical connectors from the power device can be secured directly to the upper surface of the circuit board without the need to extend them through the circuit board. Using surface mount technology, the ends of the electrical connectors are placed in contact with solid solder and the entire circuit board is assembled using a surface mount pick-and-place machine and a reflow oven in order to melt the solder and secure the connections with the electrical connector. This process eliminates the need for the leaded insertion machine and wave solder machines. Thus, surface mount technology greatly simplifies the assembly process and reduces total capital equipment costs.
In the prior art, the power device is generally positioned perpendicular to the printed circuit board, and screws are provided to connect the tabs of the power device to the PC board housing in order to dissipate heat. The screws are inserted in a direction parallel to the printed circuit board for attaching the metal tab to the housing. Of course, this attachment requires assembly time and expense. Also, the stack-up of part variations in the printed circuit board assembly requires narrow part variation tolerances for the various components of the assembly.
Accordingly, it is desirable to provide an improved method and apparatus for dissipating heat from a power device. It is further desirable to facilitate use of the surface mount technology for attachment of the power device to the printed circuit board. Additionally, it is desirable to provide a printed circuit board assembly with relaxed part tolerances for various components of the assembly.